(Swift 3,4,5...) How to Access Parts of a multipart/related HTTP Response

Demonstrates how to access the parts of a multipart/related response. This example sends a ficticious multipart/related request, and handles a ficticious multipart/related response.

We send the following multipart/related request:

Content-Type: multipart/related; start-info="text/xml"; type="application/xop+xml"; boundary="----=_Part_0_1744155.1118953559416"
Content-Length: 3453
SOAPAction: "some-SOAP-action"

------=_Part_1_4558657.1118953559446
Content-Type: application/xop+xml; type="text/xml"; charset=utf-8

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <Detail xmlns="http://example.org/mtom/data">
      <image>
        <xop:Include xmlns:xop="http://www.w3.org/2004/08/xop/include" href="cid:5aeaa450-17f0-4484-b845-a8480c363444@example.org" />
      </image>
    </Detail>
  </soap:Body>
</soap:Envelope>

------=_Part_1_4558657.1118953559446
Content-Type: image/jpeg
Content-ID: <5aeaa450-17f0-4484-b845-a8480c363444@example.org>


... binary data ...

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let http = CkoHttp()!

    let soapXml = CkoXml()!

    // Build the following SOAP XML

    // <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
    //   <soap:Body>
    //     <Detail xmlns="http://example.org/mtom/data">
    //       <image>
    //         <xop:Include xmlns:xop="http://www.w3.org/2004/08/xop/include" href="cid:5aeaa450-17f0-4484-b845-a8480c363444@example.org" />
    //       </image>
    //     </Detail>
    //   </soap:Body>
    // </soap:Envelope>

    soapXml.tag = "soap:Envelope"
    soapXml.addAttribute("xmlns:soap", value: "http://schemas.xmlsoap.org/soap/envelope/")
    soapXml.updateAttr(at: "soap:Body|Detail", autoCreate: true, attrName: "xmlns", attrValue: "http://example.org/mtom/data")
    soapXml.updateAttr(at: "soap:Body|Detail|image|xop:Include", autoCreate: true, attrName: "xmlns:xop", attrValue: "http://www.w3.org/2004/08/xop/include")
    soapXml.updateAttr(at: "soap:Body|Detail|image|xop:Include", autoCreate: true, attrName: "href", attrValue: "cid:5aeaa450-17f0-4484-b845-a8480c363444@example.org")

    soapXml.emitXmlDecl = false
    var xmlBody: String? = soapXml.getXml()
    print("\(xmlBody!)")

    let req = CkoHttpRequest()!
    req.httpVerb = "POST"
    req.path = "/something/someTarget"

    req.contentType = "multipart/related; start-info=\"text/xml\"; type=\"application/xop+xml\""
    req.addHeader("SOAPAction", value: "some-SOAP-action")

    success = req.addString(forUpload2: "", filename: "", strData: xmlBody, charset: "utf-8", contentType: "application/xop+xml; type=\"text/xml\"; charset=utf-8")

    // The bytes will be sent as binary (not base64 encoded).
    success = req.addFile(forUpload2: "", path: "qa_data/jpg/starfish.jpg", contentType: "image/jpeg")

    // The JPEG data is the 2nd sub-part, and therefore is at index 1 (the first sub-part is at index 0)
    success = req.addSubHeader(1, name: "Content-ID", value: "<5aeaa450-17f0-4484-b845-a8480c363444@example.org>")

    http.followRedirects = true

    var useTls: Bool = true
    var resp: CkoHttpResponse? = http.synchronousRequest("www.example.org", port: 443, ssl: useTls, req: req)
    if http.lastMethodSuccess != true {
        print("\(http.lastErrorText!)")
        return
    }

    // Imagine the HTTP response is multipart related and is something like this:

    // HTTP/1.1 200 OK
    // Cache-Control: no-cache, no-store
    // Pragma: no-cache
    // Transfer-Encoding: chunked
    // Content-Type: multipart/related; boundary=------------080001080500020607080905
    // Expires: -1
    // Server: Microsoft-IIS/10.0
    // X-AspNet-Version: 4.0.30319
    // X-Powered-By: ASP.NET
    // Date: Wed, 19 Feb 2020 15:27:06 GMT
    // 
    // --------------080001080500020607080905
    // Content-Type: application/xop+xml; charset=iso-8859-1
    // Content-Id: RootPart
    // Content-Transfer-Encoding: binary
    // 
    // <?xml version="1.0" encoding="iso-8859-1"?>
    // <soapenv:Envelope xmlns:xcpt="...">
    //   <soapenv:Header />
    //   <soapenv:Body>
    //     <xres:Transport profile="http://something.example.com/..." version="1.4">
    //       <xres:TransportHeader>
    // 	...
    // 	...
    //       </xres:TransportHeader>
    //       <xres:TransportBody />
    //     </xres:Transport>
    //   </soapenv:Body>
    // </soapenv:Envelope>
    // --------------080001080500020607080905--

    // To get the XML, load the full MIME of the response into a Chilkat MIME object.  Then get the body of the 1st sub-part.
    let mime = CkoMime()!
    mime.load(resp!.fullMime)

    // Your code might verify that the Content-Type is indeed multipart/related.
    print("\(mime.contentType!)")
    print("num parts = \(mime.numParts.intValue)")

    // Assuming it is, and the number of sub-parts is > 0
    if mime.numParts.intValue > 0 {
        var part0: CkoMime? = mime.getPart(0)
        // The Content-Type (in this ficticious example) should be "application/xop+xml"
        print("sub-part Content-Type: \(part0!.contentType!)")
        // Now get the XML 
        var subPartXmlBody: String? = part0!.getBodyDecoded()
        print("\(subPartXmlBody!)")
        part0 = nil
    }

    resp = nil

}